Ca2+ concentration in the peritoneal dialysis solution regulates peritoneal fibroblast proliferation and peritoneal macrophage and lymphocyte cytokine release.

Peritoneal fibrosis remains one of the major causes of dropout in continuous ambulatory peritoneal dialysis (CAPD), because it reduces ultrafiltration capacity. Since studies in vitro have demonstrated that cytoplasmic Ca2+ regulates the proliferation of most cell lines and the release of cytokines from immune cells, we evaluated in 8 uremic patients at the start of CAPD and in 4 control patients the effects in vitro of different peritoneal dialysis solution Ca concentrations (1, 1.25, 1.75, and 2 mmol/L) on peritoneal fibroblast (PF) proliferation, peritoneal macrophages (PM phi), and peritoneal lymphocyte (PLy) release of interleukin-1 (II-1) and interferon-gamma (IFN-gamma) (cytokines which are known to induce PF proliferation), and cytoplasmic Ca2+ concentration in PF, PM phi, and PLy. Results showed that in both the uremic and control patients, increasing the dose of Ca2+ in the medium induced a dose-dependent increase in PF proliferation and the release of IL-1 and IFN-gamma from PM phi and PLy. Meanwhile, the cytoplasmic parameters PF, PM phi, and PLy Ca2+ in the uremic patients were below normal; they exceeded the norm with a Ca2+ concentration of 1.75 and 2 mmol/L and were normal with a Ca2+ concentration of 1.25 mmol/L. These data suggest that in CAPD patients the use of a physiological Ca peritoneal dialysis solution (1 and 1.25 mmol/L) may be useful in reducing the proliferation of PF and the production of IL-1 and IFN-gamma thus preventing peritoneal sclerosis.